As the third generation of hardware is completed for the glider, it has reached a stage where it needs to undergo testing to find the capabilities of the glider. Below are a few tests that need to be performed on the glider and a brief explanation of each test:
- Testing of the buoyancy engine system to determine a depth rating of the glider - All of the exterior components of the glider (end-caps, switches, underwater plug etc) are rated to at least a 100m depth, whereas the buoyancy engine does not currently have a rating. A pressure test of the buoyancy engine (likely destructive) will determine the overall depth rating of the glider. (The test would be to attach all the syringes to another set of syringes with a plate on top, weight would be added to the plate until the stepper motor cannot move the weight or the seals break, if the former, the stepper motor will be upgraded.)
- Perform reliability testing of the buoyancy engine under pressure to make sure that the movement systems do not become stiff. Minimum of 24 hours.
- Perform underwater tests with the glider running at different glide angles, used to determine the best angle of attack for different missions (steeper = faster, shallower = greater endurance)
- Perform extended endurance/range testing as the current endurance/range of the glider is calculated by extrapolating out current data (42 hour running battery life at ~0.2m/s = 28km). Once a depth rating of the glider is achieved, the glider can glide to a greater depth which will mean that it reaches a greater speed and spends less of its time transitioning between gliding states, so the range of the glider will increase.
- As I have only been able to test the glider in small areas of water, it has not been possible as of yet to demonstrate the turning of the glider clearly, so the glider needs to be tested in a larger body of water.
I have also put together a to-do list to get the glider to version 3.1. This list is primarily hardware and does not include any to-do points concerning the Pixhawk and automated waypoint navigation system. An up-to-date version of this to-do list will be kept in the dropbox folder.
- Change acme nut to an anti-backlash nut to prevent acme screw wear in the long term
- Redesign wing mounts to have a slight dihedral so that the glider is more stable underwater
- Choose a standardised micro lever switch and use screws as opposed to hot glue
- Make the planetary gearbox thicker to reduce play/wear
- Redesign the wiring routes past the planetary gearbox
- Redesign the Pixhawk mounting plate so that the board can be more easily placed/removed
- Try and fit all of the external ballast bars internally, to reduce drag etc
- Change all roll components to a diameter of 98mm, as opposed to 100mm (to reduce friction inside the tubing)
- Strengthen endcap mounts to prevent bowing
- Strengthen engine bearing fastener to prevent bowing
- Redesign motor/acme clamps to increase strength
- Upgrade buoyancy engine motor to a NEMA 23 motor if required
- Make pogo PCB mounting plates thicker to prevent bowing
- Hookup the “enable” pins of the A4988 boards, so that you can power off the stepper motors when they’re not in use to increase battery life
- Hookup a greater number of the unused I/O pins to header pins to increase the number of additional sensors, etc. that can be used
- Reposition the A4988 stepper motor drivers so that you can access all of the potentiometers without drilling into the aluminium tubing
- Use the Blue Robotics switch as switch to a relay for the main power control - the switch is potentially getting to the edge of its current capability
- Think of an alternative to aluminium tubing, to reduce variability in reproduction
- Upgrade the hotend of the printer and print all components in polycarbonate
- Apply for Sparkfun funding for their dissolved oxygen sensor
- Contact Onshape on their forums with review/feedback - global parameters or feature folders are the main suggestions
- Look at using industrial pogo connector or using a plug/receptacle and signal converter
- Look at moving the motor driver for the buoyancy engine motor towards the front (in front of pogo connector) to reduce the number of wires through the cable chain